|M.Sc Student||Geva Amit|
|Subject||Investigation of a Morphing Wing Capable of Airfoil and|
Span Adjustment using a Retractable Folding
Mechanism - New Engineering Approach
|Department||Department of Aerospace Engineering||Supervisors||Professor Haim Abramovich|
|Professor Rimon Arieli|
In this research a novel concept for morphing aircraft is presented and examined. A morphing aircraft is defined as an aircraft able to perform geometry changes in its structure that allows for added attributes and abilities mid-flight. The presented aircraft is capable of alternating between two singular working points by folding the exterior surfaces of the wing underneath the interior surfaces. This folding and unfolding allows for a significant change in wingspan, lift surfaces, aspect ratio and camber.
The motivation for this type of morphing is twofold: The increase in wingspan due to unfolding, results in drag reduction and increase the endurance of the aircraft, while the opposite process, which eliminates the camber of the airfoil with contracting the segments of the wings inward, towards the center of mass, is translated into improved maneuver capabilities.
The morphing concept was exceedingly researched in the last years and numerous concepts have since been examined. However, most wingspan increasing methods have ignored the need for a separate airfoil at the different working points (or velocities), while most camber morphing concepts have achieved minimal change at a costly power and weight penalty. The solution presented in the present study, encompasses the new wing geometry, which is necessary to maintain the separate working point, by addressing both the wingspan and airfoil at the same moment, while taking into account the "cost" of additional mechanism weight.
At the first step of the study, an analysis was performed in order to assess the additional endurance gained by the morphing capabilities, compared to two standard aircraft having the two geometries. A wide spectrum of aspect ratios, wing loadings and flight scenarios were examined, while at the same time factoring in the additional weight due to the ability to morph. It was concluded that an aircraft capable of morphing can improve its endurance up to 50% compared to the standard counterparts.
An airfoil selection process was ensuing, enabling a future designer to compare the option of either selecting a proper airfoil for the folded geometry, causing a sharp-edged leading edge in the unfolded geometry, or a proper airfoil for the unfolded geometry, resulting in a leading edge gap post folding. The two options were subjected to analysis and it was concluded the latter one rather than the former one is the best option.
A wind tunnel test phase was next performed. A Clark Y 9% airfoil was chosen due to substantial leading-edge gap produced after folding and 4 models were tested, including two, which included typical methods of improving the airfoil after folding. Conclusions were drawn regarding the effect of the leading-edge gap on the aerodynamic attributes and a method capable of airfoil improvement was shown to be promising.
Finally, the folding algorithm was outlined and a typical concept for a morphing mechanism, capable of performing the folding and unfolding processes was suggested.